Examine source code of Select Some

{
  "name": "Select Some - ctrl+A but useful",
  "short_name": "Select Some",
  "description": "ctrl+a like you've never experienced before",
  "developer": {
    "name": "Michiel Dral",
    "url": "https://dral.eu/"
  },
  "version": "2",
  "manifest_version": 2,
  "permissions": [
    "tabs",
    "storage",
    "<all_urls>"
  ],
  "applications": {
    "gecko": {
      "id": "{3ff7c9aa-7b4d-4b91-b76d-7db9e13f19f9}"
    }
  },
  "background": {
    "scripts": [
      "Background/BackgroundEntry.js"
    ],
    "persistent": false
  },
  "browser_action": {},
  "content_scripts": [
    {
      "run_at": "document_end",
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "Vendor/browser-polyfill.min.js",
        "Content.js"
      ],
      "all_frames": true
    }
  ],
  "icons": {
    "16": "Icons/Icon_16.png",
    "32": "Icons/Icon_32.png",
    "64": "Icons/Icon_64.png",
    "128": "Icons/Icon_128.png"
  }
}